Haemocytometers

A haemocytometer is a specialized counting chamber used for the microscopic estimation of the number of cells in a given volume of fluid. It is a glass slide with a precisely etched grid or pattern on its surface. This grid is divided into a known area and depth, forming a chamber of a defined volume.

To use a haemocytometer, a small, known volume of a cell suspension is carefully pipetted onto the chamber. The fluid spreads evenly within the chamber due to capillary action. After allowing the cells to settle, the slide is placed under a microscope. The user then counts the number of cells within specific squares or areas of the etched grid.

By multiplying the cell count within a defined area by the reciprocal of the chamber's volume, the concentration of cells per unit volume of the original suspension can be calculated. This technique is widely employed in various scientific disciplines, including hematology for counting blood cells like red blood cells and white blood cells, microbiology for enumerating bacteria or yeast, and cell biology for determining cell viability and growth rates. Accuracy depends on proper dilution of the sample, even distribution of cells, and careful counting.